THE STRUCTURAL RELAXATION AND GLASS-TRANSITION OF LA-AL-NI AND ZR-AL-CU AMORPHOUS-ALLOYS WITH A SIGNIFICANT SUPERCOOLED LIQUID REGION

An amorphous phase with a wide supercooled liquid region, > 50 K, was found to form over wide composition ranges in the La-Al-Ni and Zr-Al-Cu systems. The largest values for the temperature span between the crystallization temperature, T(x), and the glass transition temperature, T(g), DELTAT(x) (= T(x) - T(g)), are 69 K for La55Al25Ni20 and 88 K for Zr65Al7.5Cu27.5. The structural relaxation behavior on annealing was examined for the two amorphous alloys with the largest DELTAT(x) values. The magnitude of the structural relaxation increases gradually with increasing annealing temperature, T(a), and then rapidly in the T(a) range slightly below T(g) and decreases significantly on annealing above T(g). The rapid increase in the magnitude of the structural relaxation on annealing near T(g) is due to the glass transition. The single-stage structural relaxation indicates that there is no distinct difference in relaxation times (atomic bonding forces) between the constituent atoms in the two metal-metal-type amorphous alloys. The existence of an optimum bonding state is thought to cause the wide supercooled liquid region for the two amorphous alloys.